1. Technical Field
Disclosed embodiments relate to mounting a microelectronic device on a substrate.
2. Description of Related Art
Various techniques have been tried to prepare imprinted substrates such as printed wiring boards (PWBs). As thermal management becomes more challenging due to miniaturization, dielectric particulates in the underfill material have become more important to lower the coefficient of thermal expansion (CTE) of the underfill composite. As the percentage of low CTE filler particles has increased, capillary flow of the underfill composite has become more difficult.
As the circuitry of the semiconductor devices grows smaller, lower dielectric constant insulators are needed to maintain good electrical performance. As the dielectric constant of the insulator lowers, these materials lose some of their mechanical robustness. The underfill material therefore protects the die from mechanical stress. The low CTE filler assists in this function. To assist in lowering the mechanical stress, the low CTE filler is selected to have a CTE that is close to that of the die. The advent of these highly filled underfills necessitated a closer look at the no-flow underfill process. The no-flow underfill process includes dispensing the underfill material on the substrate before attaching the die. The no-flow process experiences the entrapment of some filler particles between the solder bump and the bond pad. Consequently, the particulates decreased the quality of the electrical contact between the bond pad and the bump.